1. Field of the Invention
The invention relates to aqueous dispersions based on organosilicon compounds that can be converted into elastomers or resins following removal of water, to processes for preparing them, and to the use thereof as sealing, adhesive and coating materials.
2. Description of the Related Art
On environmental protection grounds it is appropriate to omit volatile organic constituents from chemical preparations. For this reason, the use of aqueous systems is experiencing continual increase.
Aqueous dispersions of polymers, especially those which can be converted into elastomers or resins following removal of water, are long-established. They consist essentially of a linear polymer, an emulsifier, and water. Also known, furthermore, is the addition of further substances such as crosslinkers, adhesion promoters, crosslinking catalysts, and nonreinforcing fillers. Polymers used are those having reactive end groups. Either the completed polymers can be processed directly to an emulsion, using water and emulsifier, or starting materials for the polymers are emulsified first of all, possibly followed, if desired, by an emulsion polymerization, an emulsion polycondensation, an emulsion polyaddition, or radiation-initiated or thermally initiated crosslinking. The polymer emulsion may then be mixed with a crosslinker component and catalysts, in each case in bulk or in the form of an emulsion, and also with further constituents, such as fillers, adhesion promoters, etc.
Aqueous dispersions of organopolysiloxanes have to date been stabilized generally by means of organic emulsifiers. Cationic, anionic, ampholytic and nonionic emulsifiers are all used. An exemplary specification that may be mentioned here includes EP 365 439 A.
U.S. Pat. No. 4,221,688 and U.S. Pat. No. 4,427,811 describe silicone polymer emulsions which cure to elastomers on removal of water and are stabilized by anionic emulsifiers. These emulsions further comprise colloidal silicon dioxide for the purpose of enhancing the mechanical properties. In U.S. Pat. No. 5,162,429, moreover, silicone polymer emulsions are described that consist of a polymer emulsion stabilized with anionic emulsifier and fumed silica dispersion stabilized with anionic emulsifier, in water. The fumed silica in that case serves as a reinforcing filler.
For areas of application where surface-active substances, such as emulsifiers, alter the typical silicone properties, no suitable solution has yet been disclosed, since aqueous systems fundamentally include such emulsifiers at present. These substances have consequences for surface properties as well, such as for the wettability, for example.